Tissue proximity indicator threshold for cardiac ablation

Abstract

The system provides a mechanism in which the tissue proximity indicator threshold is dynamically adjusted for each patient (and optionally for each cardiac position). [Solution] The solution includes a catheter 14 including an electrode 26 for providing an intracardiac electrogram (IEGM) signal and a signal for sensing impedance; an ablation energy generator for conducting ablation energy to the electrode of the catheter; a controller 30 for sampling the IEGM signal from the electrode before and after ablation and sensing the impedance between the electrode and the tissue; and a processor 56 for comparing the sensed impedance with a TPI threshold, rendering an index of the electrode's contact status with the determined tissue on a display 27, calculating the change in the IEGM signal due to the ablation, and adjusting the TPI threshold for subsequent ablation based on the calculated change in the IEGM signal due to a given ablation of the tissue using the electrode.

Description

Technical Field

[0001] The present disclosure relates to ablation using a therapeutic intracardiac catheter, and more particularly, but not limited to, tissue proximity indicators during cardiac ablation.

Background Art

[0002] A wide range of medical procedures involve placing a probe, such as a catheter, inside a patient's body. One medical procedure in which these types of probes or catheters have proven extremely useful is in the treatment of cardiac arrhythmias. Cardiac arrhythmias and atrial fibrillation in particular persist as dangerous medical conditions that are common, especially in the elderly population.

[0003] Diagnosis and treatment of cardiac arrhythmias include mapping the electrical properties of cardiac tissue, particularly the endocardium and cardiac volume, and selectively ablating cardiac tissue by applying energy. A catheter is inserted into the heart cavity during such a procedure and optionally around the heart cavity. In most procedures, multiple catheters are inserted into the patient. Catheters can include mapping catheters, ablation catheters, temperature sensing catheters, and image sensing catheters. Some catheters are dedicated to placement in specific parts of the anatomical structure, such as the coronary sinus, esophagus, atrium, or ventricle. Catheters have multiple electrical channels, and some have more channels than other catheters depending on the number of sensors and electrodes included in each catheter. The number and type of catheters are determined according to the procedure and the workflow preferred by the physician.

[0004] A typical ablation procedure involves inserting a catheter with one or more electrodes at its distal end into the cardiac chamber. A radio frequency (RF) current (or pulsed-field ablation, PFA) energy) is applied through the tip electrode of the ablation catheter, causing the current to flow through the surrounding medium between the tip electrode and the indifferent electrode, namely the blood and tissue. The current distribution is determined by the amount of electrode surface in contact with the tissue compared to the blood, which has higher conductivity than the tissue. Heating of the tissue occurs due to its electrical resistance. When the tissue is sufficiently heated, cell destruction occurs in the cardiac tissue, resulting in the formation of electrically nonconductive lesions within the cardiac tissue.

[0005] Therefore, when placing an ablation or other catheter inside the body, specifically near the endocardial tissue, it is desirable to have the ablation electrode of the catheter in direct contact with the tissue. Electrode-tissue contact can be measured based on the impedance between the electrode at the distal end of the catheter and the return electrode. [Brief explanation of the drawing]

[0006] This disclosure will be understood from the following detailed description in conjunction with the attached drawings. [Figure 1] This is a simplified diagram of a catheter-based electrophysiological mapping and ablation system constructed and operating according to the examples of this disclosure. [Figure 2] This is a more detailed isometric view of the expandable distal end assembly of the catheter used in the system shown in Figure 1. [Figure 3] This is a simplified qualitative diagram showing the impedance measured by an electrode within a body cavity as a function of the proximal distance of the electrode from the cavity wall tissue, for use in the system shown in Figure 1. [Figure 4A] This is a flowchart showing the steps for adjusting the tissue proximity indicator threshold for use in the system shown in Figure 1. [Figure 4B]This is a flowchart showing the steps for adjusting the tissue proximity indicator threshold for use in the system shown in Figure 1. [Modes for carrying out the invention]

[0007] overview As mentioned above, contact between an electrode and tissue can be measured based on the impedance between the electrode and the tissue. The quality of contact between the electrode and tissue can be expressed as a tissue proximity indicator (TPI). A specific patient's TPI threshold can be used, for example, to determine whether the electrode is in sufficient contact with the tissue for a successful ablation. From a physician's perspective, it is generally important to consider whether the electrode is in sufficient contact with the tissue if the cardiac signal at the ablation site is sufficiently attenuated by the ablation. If the cardiac signal in the tissue is sufficiently attenuated by the ablation, then the electrode was in sufficient contact with the tissue during the ablation.

[0008] The TPI threshold, which may be selected, defines whether a given impedance value indicates sufficient contact to adequately attenuate the cardiac signal. For example, if the sensed impedance is greater than the threshold TPI, the sensed impedance indicates that the electrode is in sufficient contact with the tissue and will successfully ablate it, while if the sensed impedance is not greater than the TPI threshold, the sensed impedance indicates that the electrode is not in sufficient contact with the tissue. Therefore, it is important that the TPI threshold is carefully selected to indicate the quality of contact necessary for ablation success, e.g., to achieve the desired damage.

[0009] In reality, the TPI threshold required to achieve the desired injury is generally patient-dependent and also location-dependent. Therefore, having a general TPI threshold does not provide a good indicator of "contact" between the electrode and the tissue. For example, a physician may use one TPI threshold to ablate around the pulmonary veins (PV) and another TPI threshold to ablate the apex of the atria. In another example, a physician may use one TPI threshold to ablate the left superior PV (LSPV) and another TPI threshold to ablate the right inferior PV (RIPV). Furthermore, physicians may use significantly different TPI thresholds from patient to patient.

[0010] An example of the present disclosure addresses at least some of the above challenges by providing a system in which the TPI threshold is dynamically adjusted for each patient (and optionally for each cardiac location). For example, one TPI threshold may be dynamically adjusted for patient X for PV, and another TPI threshold may be dynamically adjusted for patient X for RIPV.

[0011] First, a TPI threshold can be estimated. The disclosed example illustrates a method for estimating an initial TPI threshold based on minimum and maximum impedance. The system samples an intracardiac electrogram (IEGM) sensed by an electrode and also performs impedance measurements to measure the impedance between the electrode and the tissue. The IEGM may be sensed between the electrode and another catheter electrode or one or more surface electrodes. The system measures the impedance and compares it to the TPI threshold to determine the contact status of the electrode. For example, if the impedance is greater than the TPI threshold, the contact status is considered to be sufficient; if the measured impedance is less than the TPI threshold, the contact status is considered to be insufficient. The contact status may be rendered on a display screen for the physician to view.

[0012] The physician decides to perform ablation at the current electrode position based on one or more factors. The system samples the IEGM, performs the ablation, and samples the IEGM again after the ablation to determine the decrease in IEGM (amplitude or other measurement) due to the ablation. The decrease in IEGM may be defined as the decrease in the magnitude of the inter-peak voltage after ablation compared to before ablation. The TPI threshold adjustment is defined as a function of the magnitude of the decrease in IEGM, or alternatively, as a function of the rate of decrease in voltage due to ablation. If the decrease in IEGM exceeds a given decrease, the TPI threshold is decreased based on the decrease in IEGM. If the decrease in IEGM is less than or equal to the given decrease, the TPI threshold may be increased. The new TPI threshold may be calculated using the following formula. New TPI threshold = Old TPI threshold - (DeltaV - B)A In the formula, DeltaV is the decrease in the voltage amplitude of the IEGM due to ablation, and A and B are threshold adjustment coefficients. A and B are selected to achieve a gradual change in the TPI threshold toward a target TPI threshold toward achieving the desired damage using ablation. For example, if DeltaV is expected to be about 4 millivolts, B may be about 0.3 or 0.4 and A may be about 5, for example. However, any suitable values ​​for A and B may be selected by the user, for example. The above steps may be repeated at different ablation sites so that the TPI threshold can be adjusted after the success of each ablation.

[0013] The TPI threshold can be electrode-specific, and thereafter, the electrode-specific TPI threshold is dynamically adjusted based on the data collected for a given electrode. In some cases, the TPI threshold may be common to all electrodes (or a subset of electrodes), and consequently, the common TPI threshold is dynamically adjusted based on the data collected for any given electrode (of a catheter or a subset of electrodes).

[0014] In some cases, the physician may choose to reset the TPI threshold to its original (pre-adjustment) threshold at any time. Optionally, the system may reset the TPI threshold if the distance between two subsequent ablation sites exceeds a predetermined distance. This predetermined distance can be defined by the user (e.g., the physician) or the system. In this way, the system does not require an excessive amount of contact force without reason.

[0015] System Description Referring to Figure 1, Figure 1 is a simplified diagram of a catheter-based electrophysiological mapping and ablation system according to an embodiment of the subject matter of this disclosure, showing an exemplary catheter-based electrophysiological mapping and ablation system 10. Referring also to Figure 2, Figure 2 is a detailed isometric view of the expandable distal end assembly 28 of the catheter 14 of Figure 1.

[0016] System 10 includes a plurality of catheters that are percutaneously inserted by a physician 24 (as can be seen in inset 45) into the lumen or vascular structure of the heart 12 through the patient's vascular system. Typically, a delivery sheath catheter is inserted into the left or right atrium near a desired location in the heart 12. One or more catheters can then be inserted into the delivery sheath catheter to reach a desired location in the heart 12. The plurality of catheters may include a catheter dedicated to sensing intracardiac electrophysiography (IEGM) signals, a catheter dedicated to ablation, and / or a catheter dedicated to both sensing and ablation. An exemplary catheter 14 configured to sense IEGM is illustrated herein. To sense a target site in the heart 12, the physician 24 may position the distal end assembly 28 of the catheter 14 in contact with the heart wall. For ablation, the physician 24 may similarly position the distal end of an ablation catheter in contact with a target site for tissue ablation.

[0017] As seen in inset 65, the catheter 14 is an exemplary catheter comprising one, and preferably more, electrodes 26 distributed across a plurality of splines 22 in an optionally expandable distal end assembly 28 and configured to sense IEGM signals. The catheter 14 additionally comprises (i) a proximal position sensor 29 comprising two or three electromagnetic coils (EMCs) embedded in the distal end 46 of a shaft 44 near the expandable distal end assembly 28, and (ii) optionally one or more distal position sensors 39 for tracking the position of the distal end of the expandable distal end assembly 28. Optionally, and preferably, the position sensors 29 and 39 are magnetic-based position sensors. The inset also shows the longitudinal axis 42 of the catheter 14 and the distal edge 16 of the distal end assembly 28. Alternatively, the catheter 14 has an elongated distal end comprising a plurality of ring-shaped electrodes. In this exemplary catheter, the elongated distal end is configured, in its neutral position, to form a loop of such size and shape as, for example, that is positioned around the openings of the four pulmonary veins extending from the patient's left atrium.

[0018] Figure 2 provides enlarged views of insets 45 and 65, showing an expandable distal end assembly 28 in contact with the tissue 80 of the heart 12.

[0019] A magnetic-based position sensor may operate in conjunction with a position pad 25 which includes multiple magnetic coils 32 configured to generate a magnetic field within a predefined working volume. The real-time position of the distal end assembly 28 of the catheter 14 may be tracked based on the magnetic field generated by the position pad 25 and sensed by the magnetic-based position sensor. Details of magnetic-based position sensing technology are described in U.S. Patents No. 5,391,199, No. 5,443,489, No. 5,558,091, No. 6,172,499, No. 6,239,724, No. 6,332,089, No. 6,484,118, No. 6,618,612, No. 6,690,963, No. 6,788,967, and No. 6,892,091.

[0020] System 10 may include one or more electrode patches 38 positioned to contact the skin on patient 23 to establish a position reference for position pad 25 and impedance-based tracking of electrodes 26. For impedance sensing, current is directed to electrodes 26 and sensed at electrode skin patches 38 or between a pair of electrodes 26.

[0021] Recorder 11 may record and display electrogram 21 captured by body surface ECG electrodes 18 and intracardiac electrogram (IEGM) captured by electrodes 26 of catheter 14. Recorder 11 may include pacing capabilities for pacing the rhythm of the heart and / or may be electrically connected to an independent pacer. System 10 may include an ablation energy generator 50 adapted to conduct ablation energy to one or more of the electrodes at the distal tip of a catheter configured to ablate. The energy generated by ablation energy generator 50 may include radiofrequency (RF) energy, or pulsed field ablation (PFA) energy including unipolar or bipolar high voltage DC pulses such as may be used to perform irreversible electroporation (IRE), or combinations thereof, but is not limited thereto.

[0022] Patient interface unit (PIU) 30 is an interface configured to establish electrical communication between the catheter, other electrophysiological devices, a power source, and a workstation 55 for controlling the operation of system 10. The electrophysiological devices of system 10 may include, for example, multiple catheters, position pad 25, body surface ECG electrodes 18, electrode patches 38, ablation energy generator 50, and recorder 11. Optionally and preferably, PIU 30 additionally includes processing capabilities for implementing real-time calculation of the position of the catheter and performing ECG calculations.

[0023] The workstation 55 includes a memory 57, a processor unit 56 having a memory or storage device in which appropriate operating software is stored, and a user interface function. The workstation 55 may optionally provide a plurality of functions including: (1) Rendering a 3D graphical representation of a model or anatomical map 20 to model the endocardial anatomical structure in three dimensions (3D) and display it on the display device 27; (2) Displaying, on the display device 27, an activation sequence (or other data) compiled from the recorded potential map 21 as a representative visual mark or image superimposed on the rendered anatomical map 20; (3) Rendering a 3D graphical representation of a model to model a catheter inserted into the body in three dimensions (3D) and display it on the display device 27; (4) Displaying the real-time positions and orientations of a plurality of catheters within the heart chamber; (5) Displaying a target site, such as a location where ablation energy has been applied, on the display device 27.

[0024] One commercially available product embodying the elements of the system 10 is available as the CARTO (trademark) 3 system, marketed by Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0025] Note that tissue impedance typically exceeds blood impedance, and impedance values exceeding blood impedance are expected to be measured at electrodes closer to the tissue than at electrodes immersed in the blood away from the tissue wall. In some embodiments, tissue proximity is based on patient-specific minimum and maximum impedance values measured in the patient.

[0026] Referring here to Figure 3, which is a simplified qualitative diagram showing the impedance measured by an electrode in a body cavity as a function of distance from the cavity wall structure 80, according to one aspect of the present disclosure. Figure 3 shows a graph having a qualitative proximity value (e.g., TPI) of proximity to the cavity wall structure 80 on the X axis 302 and impedance values ​​on the Y axis 304. The graph in Figure 3 includes a line 306 showing the impedance value of the electrode in the body cavity as a function of qualitative proximity to the cavity wall, and a continuation of line 306 to the region where the electrode contacts the cavity wall at varying pressures.

[0027] The graph in Figure 3 shows the expected impedance behavior within the body cavity as a function of proximity. Note that as the distance to the cavity wall decreases, the proximity to the cavity wall increases. The graph in Figure 3 shows the expected shape of the relationship between impedance and proximity.

[0028] In some exemplary modes, in vivo measurements may determine the impedance values ​​at endpoints, as well as minimum and maximum values. Such minimum and maximum values ​​may be determined patient-specifically by optionally accumulating data in real time and determining the minimum and maximum values ​​of the real-time data.

[0029] It should be noted that the minimum and maximum impedance values ​​for each electrode are, in particular, functions of the distance of the electrode to the reference electrode. In some embodiments, the minimum and maximum impedance values ​​for each electrode are adjusted to determine normalized minimum and maximum impedance values ​​for all electrodes.

[0030] In some embodiments, data points for constructing line 306 are optionally measured in vivo by electrodes moving within a body cavity to measure impedance. All or at least some of the measurements are used to generate line 306.

[0031] In some embodiments, only the maximum and minimum impedance values ​​are determined by in vivo measurements, optionally and patient-specifically. In some embodiments, data points for constructing line 306 are measured in vivo by several electrodes moving within a body cavity to measure impedance, optionally, and by a position measuring system to measure the position of the electrodes.

[0032] In some embodiments, data points for constructing line 306 are optionally obtained from a database containing data measured at some point in the past for a particular patient. In some embodiments, data points for constructing line 306 are optionally obtained from a database containing data measured at some point in the past for an optionally averaged group of patients.

[0033] Figure 3 also shows two specific levels of impedance along the Y-axis 304. The first specific impedance level 308 represents an impedance close to zero at a distance to the cavity wall, such as when the electrode begins to touch the cavity wall. The line 306 to the left of the contact impedance is within the "non-contact" impedance zone 312. In some embodiments, the value of the first specific impedance level 308 is determined as a specific percentage below the maximum value of line 306.

[0034] A second specific impedance level 310 represents the impedance of the electrode touching and pushing against the cavity wall, at a force level considered sufficient to perform ablation using the electrode, if desired. A corresponding “contact” zone 314 is shown, where the cavity wall is pushed somewhat from the contact point due to a greater force being applied to the cavity wall to produce a sufficiently good contact. Beyond the “contact” zone 314, the impedance flattens out and reaches its maximum value, which is indicated by the “saturation” zone 316 and the high impedance above the level referred to by 310.

[0035] Referring now to Figures 4A and 4B, Figures 4A and 4B are flowcharts 400 that include steps in a method for adjusting the tissue proximity indicator for use in the system of Figure 1. First, the steps shown in Figure 4A will be described.

[0036] In some embodiments, the processor unit 56 is configured to identify minimum and maximum impedances and corresponding minimum and maximum TPI limits (block 402) using the method described above, for example with reference to Figure 3, and to define an estimated TPI threshold (block 404) such that it lies between the minimum and maximum TPI limits and is based on a function of the minimum and maximum TPI limits. In some embodiments, the estimated TPI threshold may be defined as a given distance from the minimum or maximum, or as a given ratio between the minimum and maximum TPI limits.

[0037] In some embodiments, the processor unit 56 is configured to receive user input (block 406) for determining threshold adjustment parameters A and B, as will be described in more detail below.

[0038] The PIU 30 (or any preferred controller) is configured to sample an intracardiac electrogram (IEGM) signal from a given electrode (e.g., one of the electrodes 26) (block 408) (for example, before ablation at the target tissue site), and to sense the impedance between the given electrode 26 and the tissue 80 based on the impedance measured between the given electrode 26 and another catheter electrode 26 or body surface electrode 18 (block 410). The catheter 14 (Figure 1) includes a given electrode 26 that provides the IEGM signal and a signal used to sense the impedance between the given electrode 26 and the tissue 80.

[0039] The processor unit 56 is configured to determine the contact status of a given electrode 26 with respect to the tissue 80 by comparing the measured impedance with an estimated or current TPI threshold (block 414). In some embodiments, if the measured impedance is less than or equal to the TPI threshold, the contact status is non-contact; however, if the measured impedance is greater than or equal to the TPI threshold, the contact status is contact. In other embodiments, if the measured impedance is less than the TPI threshold, the contact status is non-contact; however, if the measured impedance is greater than or equal to the TPI threshold, the contact status is contact. The contact status indicates whether a given electrode 26 is close enough to the tissue 80 to cause a predetermined reduction in the IEGM signal resulting from ablation. The reduction in the IEGM signal can be defined as the reduction in the IEGM signal measured after ablation compared to a measurement performed before ablation, based on peak-to-peak measurements of the IEGM signal within a window of interest of the IEGM signal.

[0040] The processor unit 56 is configured to render an indicator of the contact status of a given electrode with respect to tissue on a display device 27 (block 416). The indicator may include text values ​​(e.g., "in contact" or "not in contact") and / or color values ​​(e.g., "red" if not in contact, "green" if in contact).

[0041] Now, let's explain the steps shown in Figure 4B.

[0042] The ablation energy generator 50 is configured to conduct ablation energy to a given electrode 26 of the catheter 14 based on user input, typically under the control of a physician 24, and the processor unit 56 is configured to check the stability of the movement of a given electrode 26 during ablation, for example by monitoring the position of a given electrode 26 during ablation (block 418).

[0043] In some embodiments, in decision block 420, the processor unit 56 determines whether the stability of a given electrode 26 is within a given limit (e.g., user-defined). If the stability of the given electrode 26 is not within the given limit, the method returns to the step in block 408 shown in Figure 4A, where the processor unit 56 is configured to sample the IEGM signal from the given electrode 26 before another ablation (e.g., at a different ablation site). If the stability of the given electrode 26 is within the given limit, the method continues to the step in block 422.

[0044] The PIU30 (or any preferred controller) is configured to sample an intracardiac electrogram (IEGM) signal from a given electrode 26 (block 422) (for example, after ablation at the target tissue site), and the processing unit is configured to calculate the change in the IEGM signal (peak-to-peak voltage) resulting from the current ablation.

[0045] The processor unit 56 is configured to adjust the TPI threshold for subsequent ablations based on the calculated change in the IEGM signal resulting from the current ablation of tissue 80 using a given electrode 26 (block 426). Thus, if the stability of a given electrode is checked in the step of block 418, the step of block 426 depends on the stability of the movement of the given electrode 26 being within a given limit. The TPI threshold is adjusted based on the decrease in IEGM. If the observed decrease in IEGM exceeds a given decrease, the TPI threshold is decreased based on the decrease in IEGM. If the observed decrease in IEGM is less than or equal to a given decrease, the TPI threshold may be increased. The adjustment of the TPI threshold allows for gradual adjustment of the TPI threshold until it reaches or approaches a target TPI threshold. A new TPI threshold may be calculated using the following formula. New TPI threshold = Old TPI threshold - (DeltaV - B)A In the formula, DeltaV is the decrease in the voltage amplitude of the IEGM due to ablation, and A and B are threshold adjustment coefficients. A and B are selected to gradually change the TPI threshold toward the target "actual" TPI threshold. For example, if DeltaV is expected to be about 4 millivolts, then B may be about 0.3 or 0.4 and A may be about 5, for example. However, any suitable values ​​for A and B may be selected by the user, for example.

[0046] In some exemplary modes, the processor unit 56 is configured to adjust the TPI threshold for each electrode 26 of the catheter 14. In other words, the system 10 manages multiple TPI thresholds that are specific to the electrodes and adjusted based on the data of each electrode 26. In other exemplary modes, the processor unit 56 is configured to adjust the TPI threshold so that the same TPI threshold is maintained for multiple electrodes 26 of the catheter 14.

[0047] The processor unit 56 is configured to iteratively adjust the TPI threshold based on each previous TPI threshold and each reduction in the voltage of the IEGM signal resulting from the ablation at each ablation site. In other words, the steps in blocks 408-426 are repeated at different ablation sites, and the TPI threshold may be adjusted in the step in block 426 after each ablation to converge toward an optimal TPI threshold that best represents the proximity required to achieve the desired reduction in peak-to-peak IEGM voltage resulting from the ablation (or desired damage).

[0048] In practice, some or all of these functions of the processor unit 56 may be combined into a single physical component or embodied using multiple physical components. These physical components may include hardwired devices, programmable devices, or a combination of the two. In some embodiments, at least some of the functions of the processor unit 56 may be executed by a programmable processor under the control of suitable software. This software may be downloaded to the device in electronic form, for example, via a network. Alternatively or additionally, this software may be stored in a tangible, non-temporary computer-readable storage medium such as optical memory, magnetic memory, or electronic memory.

[0049] As used herein, the terms “about” or “approximately” for any number or range of numbers indicate a suitable dimensional tolerance that enables some or a set of components to function for their intended purpose as described herein. More specifically, “about” or “approximately” may refer to a range of values ​​within ±20% of the enumerated values; for example, “about 90%” may refer to a range of values ​​between 72% and 108%. [Examples]

[0050] Example 1: An apparatus comprising: a catheter including electrodes for providing signals used to sense intracardiac electromagnetism (IEGM) signals and impedance; an ablation energy generator configured to conduct ablation energy to the electrodes of the catheter based on user input; a controller configured to sample IEGM signals from the electrodes before and after a given ablation and to sense the impedance between the electrodes and tissue; and a processor configured to compare the sensed impedance with a TPI threshold to determine the contact status of the electrodes with the tissue, render an index of the determined contact status on a display, calculate the change in the IEGM signal resulting from a given ablation, and adjust the TPI threshold for subsequent ablations based on the calculated change in the IEGM signal resulting from a given ablation of tissue using the electrodes.

[0051] Example 2: The apparatus according to Example 1, wherein the processor is configured to iteratively adjust the TPI threshold based on each previous TPI threshold and each decrease in the voltage of the IEGM signal resulting from ablation at each ablation site.

[0052] Example 3: The apparatus according to Example 1 or 2, wherein the processor is configured to check the stability of electrode movement during ablation and adjust the TPI threshold based on the fact that the stability of electrode movement is within a given limit.

[0053] Example 4: The apparatus according to any one of Examples 1 to 3, wherein the processor is configured to reduce the TPI threshold based on observing at least a given reduction in the IEGM signal resulting from tissue ablation using electrodes.

[0054] Example 5: The apparatus according to any one of Examples 1 to 3, wherein the processor is configured to increase the TPI threshold based on observing a decrease in the IEGM signal resulting from tissue ablation using electrodes.

[0055] Example 6: The apparatus according to any one of Examples 1 to 5, wherein the processor is configured to receive user input and determine a threshold adjustment coefficient.

[0056] Example 7: The apparatus according to any one of Examples 1 to 6, wherein the processor is configured to identify minimum impedance and maximum impedance and corresponding minimum TPI limit and maximum TPI limit, and to define an estimated TPI threshold such that it lies between the minimum TPI limit and the maximum TPI limit, and based on a function of the minimum TPI limit and the maximum TPI limit.

[0057] Example 8: The apparatus according to any one of Examples 1 to 7, wherein the processor is configured to adjust the TPI threshold for each electrode of the catheter.

[0058] Example 9: The apparatus according to any one of Examples 1 to 7, wherein the processor is configured to adjust the TPI threshold so that the same TPI threshold is maintained for multiple electrodes of the catheter.

[0059] Example 10: The apparatus according to any one of Examples 1 to 9, wherein the processor is configured to calculate a new TPI threshold based on a value obtained by subtracting a first coefficient from the previous TPI threshold and multiplying that value by subtracting a second coefficient from the voltage drop of the IEGM signal.

[0060] Example 11: A method comprising: providing a signal used to sense intracardiac electrogram (IEGM) signals and impedance by electrodes of a catheter; conducting ablation energy to the electrodes of the catheter based on user input; sampling IEGM signals from the electrodes before and after a given ablation; sensing impedance between the electrodes and tissue; comparing the sensed impedance with a TPI threshold to determine the contact status of the electrodes with the tissue; rendering an index of the determined contact status on a display; calculating a change in the IEGM signal resulting from a given ablation; and adjusting the TPI threshold for subsequent ablations based on the calculated change in the IEGM signal resulting from a given ablation of tissue using electrodes.

[0061] Example 12: The method according to Example 11, further comprising iteratively adjusting the TPI threshold based on each previous TPI threshold and each decrease in the voltage of the IEGM signal resulting from ablation at each ablation site.

[0062] Example 13: The method according to Example 11 or 12, further comprising checking the stability of electrode migration during ablation, and adjusting the TPI threshold based on the fact that the stability of electrode migration is within a given limit.

[0063] Example 14: The method according to any one of Examples 11 to 13, further comprising reducing the TPI threshold based on observing at least a given decrease in the IEGM signal resulting from tissue ablation using electrodes.

[0064] Example 15: The method according to any one of Examples 11 to 13, further comprising increasing the TPI threshold based on observing less than a given decrease in the IEGM signal resulting from tissue ablation using electrodes.

[0065] Example 16: The method according to any one of Examples 11 to 15, further comprising receiving user input and determining a threshold adjustment coefficient.

[0066] Example 17: The method of any one of Examples 11 to 16, further comprising identifying the minimum impedance and maximum impedance and the corresponding minimum TPI limit and maximum TPI limit, and defining an estimated TPI threshold such that it lies between the minimum TPI limit and the maximum TPI limit, and based on a function of the minimum TPI limit and the maximum TPI limit.

[0067] Example 18: The method according to any one of Examples 11-17, wherein the adjustment includes adjusting the TPI threshold for each electrode of the catheter.

[0068] Example 19: The method according to any one of Examples 11-17, wherein the adjustment includes adjusting the TPI threshold so that the same TPI threshold is maintained for multiple electrodes of the catheter.

[0069] Example 20: The method according to any one of Examples 11 to 19, further comprising calculating a new TPI threshold based on a value obtained by subtracting a first coefficient from the previous TPI threshold and multiplying that value by subtracting a second coefficient from the voltage drop of the IEGM signal.

[0070] For clarity, various features of the present disclosure described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, for brevity, various features of the present disclosure described in the context of a single embodiment may also be provided separately or in any preferred partial combination.

[0071] The embodiments described above are cited as examples, and this disclosure is not limited to those specifically illustrated and described above. Rather, the scope of this disclosure includes both combinations and partial combinations of the various features described above, as well as variations and modifications thereof not disclosed in the prior art, which would be conceivable to those skilled in the art by reading the above description.

[0072] [Implementation Method] (1) A catheter including electrodes for providing signals used to sense intracardiac electromagnetism (IEGM) signals and impedance, An ablation energy generator configured to conduct ablation energy to the electrodes of the catheter based on user input, It is a controller, The IEGM signal from the electrode is sampled before and after a given ablation. A controller configured to sense the impedance between the electrode and the tissue, It is a processor, The sensed impedance is compared with the TPI threshold to determine the contact status of the electrode with the tissue. The indicators of the determined contact situation are rendered on the display. The change in the IEGM signal caused by the given ablation is calculated, An apparatus comprising: a processor configured to adjust the TPI threshold for subsequent ablation based on the calculated change in the IEGM signal resulting from the given ablation of the tissue using the electrodes. (2) The apparatus according to Embodiment 1, wherein the processor is configured to iteratively adjust the TPI threshold based on each previous TPI threshold and each decrease in the voltage of the IEGM signal resulting from ablation at each ablation site. (3) The processor The stability of the electrode's movement during ablation is checked, The apparatus according to Embodiment 1, configured to adjust the TPI threshold based on the stability of the electrode movement being within a given limit. (4) The apparatus according to Embodiment 1, wherein the processor is configured to reduce the TPI threshold based on observing at least a given reduction in the IEGM signal resulting from ablation of the tissue using the electrodes. (5) The apparatus according to Embodiment 1, wherein the processor is configured to increase the TPI threshold based on observation of a decrease in the IEGM signal less than a given decrease resulting from ablation of the tissue using the electrodes.

[0073] (6) The apparatus according to Embodiment 1, wherein the processor is configured to receive user input and determine a threshold adjustment coefficient. (7) The processor Identify the minimum and maximum impedance, and the corresponding minimum and maximum TPI limits. The apparatus according to Embodiment 1, wherein the estimated TPI threshold is defined such that it lies between the minimum TPI limit and the maximum TPI limit, and is defined based on a function of the minimum TPI limit and the maximum TPI limit. (8) The apparatus according to Embodiment 1, wherein the processor is configured to adjust the TPI threshold for each electrode of the catheter. (9) The apparatus according to Embodiment 1, wherein the processor is configured to adjust the TPI threshold so that the same TPI threshold is maintained for multiple electrodes of the catheter. (10) The apparatus according to Embodiment 1, wherein the processor is configured to calculate a new TPI threshold based on a value obtained by multiplying the value obtained by subtracting a first coefficient from the previous TPI threshold by a value obtained by subtracting a second coefficient from the voltage drop of the IEGM signal.

[0074] (11) To provide signals used to sense intracardiac electromagnetism (IEGM) signals and impedance via electrodes of a catheter, Based on user input, ablation energy is transmitted to the electrodes of the catheter, Sampling the IEGM signal from the electrode before and after a given ablation, To sense the impedance between the electrode and the tissue, The sensed impedance is compared with the TPI threshold to determine the contact status of the electrode with the tissue, The determined indicators of the contact situation are rendered on the display, To calculate the change in the IEGM signal caused by the given ablation, A method comprising adjusting the TPI threshold for subsequent ablation based on the calculated change in the IEGM signal resulting from the given ablation of the tissue using the electrodes. (12) The method according to Embodiment 11, further comprising iteratively adjusting the TPI threshold based on each previous TPI threshold and each decrease in the voltage of the IEGM signal resulting from ablation at each ablation site. (13) The method according to Embodiment 11, further comprising checking the stability of the movement of the electrode during ablation, wherein the adjustment includes adjusting the TPI threshold on the basis that the stability of the movement of the electrode is within a given limit. (14) The method according to Embodiment 11, further comprising reducing the TPI threshold based on observing at least a given decrease in the IEGM signal resulting from ablation of the tissue using the electrodes. (15) The method according to embodiment 11, further comprising increasing the TPI threshold based on observing less than a given decrease in the IEGM signal resulting from ablation of the tissue using the electrodes.

[0075] (16) The method according to embodiment 11, further comprising receiving user input and determining a threshold adjustment coefficient. (17) Identifying the minimum impedance and maximum impedance and the corresponding minimum TPI limit and maximum TPI limit, The method according to Embodiment 11, further comprising defining an estimated TPI threshold such that it lies between the minimum TPI limit and the maximum TPI limit, and based on a function of the minimum TPI limit and the maximum TPI limit. (18) The method according to embodiment 11, wherein the adjustment includes adjusting the TPI threshold for each electrode of the catheter. (19) The method according to Embodiment 11, wherein the adjustment includes adjusting the TPI threshold so that the same TPI threshold is maintained for multiple electrodes of the catheter. (20) The method according to Embodiment 11, further comprising calculating a new TPI threshold based on a value obtained by subtracting a first coefficient from the previous TPI threshold and multiplying that value by a value obtained by subtracting a second coefficient from the voltage drop of the IEGM signal.

Claims

1. A catheter (14) including an electrode (26) for providing signals used to sense intracardiac electromagnetism (IEGM) signals and impedance, An ablation energy generator (50) configured to conduct ablation energy to the electrode (26) of the catheter (14) based on user input, Controller (30), The IEGM signal from the electrode (26) is sampled before and after a given ablation. A controller (30) is configured to sense the impedance between the electrode (26) and the tissue (80), A processor (56), The detected impedance is compared with a tissue proximity indicator (TPI) threshold to determine the contact status of the electrode (26) with the tissue (80). The indicator of the determined contact situation is rendered on the display (27), The change in the IEGM signal caused by the given ablation is calculated. An apparatus comprising: a processor (56) configured to adjust the TPI threshold for subsequent ablation based on the calculated change in the IEGM signal resulting from the given ablation of the tissue (80) using the electrode (26).

2. The apparatus according to claim 1, wherein the processor (56) is configured to iteratively adjust the TPI threshold based on each previous TPI threshold and each decrease in the voltage of the IEGM signal resulting from the ablation at each ablation site.

3. The aforementioned processor (56) The stability of the movement of the electrode (26) during ablation is checked, The apparatus according to claim 1, configured to adjust the TPI threshold based on the fact that the stability of the movement of the electrode (26) is within a given limit.

4. The apparatus according to claim 1, wherein the processor (56) is configured to reduce the TPI threshold based on observing at least a given decrease in the IEGM signal resulting from ablation of the tissue (80) using the electrode (26).

5. The apparatus according to claim 1, wherein the processor (56) is configured to increase the TPI threshold based on observations of a decrease in the IEGM signal less than a given decrease due to ablation of the tissue (80) using the electrode (26).

6. The apparatus according to claim 1, wherein the processor (56) is configured to receive user input and determine a threshold adjustment coefficient.

7. The aforementioned processor (56) Identify the minimum and maximum impedances and the corresponding minimum and maximum TPI limits. The apparatus according to claim 1, wherein the estimated TPI threshold is defined such that it lies between the minimum TPI limit and the maximum TPI limit, and is defined based on a function of the minimum TPI limit and the maximum TPI limit.

8. The apparatus according to claim 1, wherein the processor (56) is configured to adjust the TPI threshold for each electrode (26) of the catheter (14).

9. The apparatus according to claim 1, wherein the processor (56) is configured to adjust the TPI threshold so that the same TPI threshold is maintained for a plurality of electrodes (26) of the catheter (14).

10. The apparatus according to any one of claims 1 to 9, wherein the processor (56) is configured to calculate a new TPI threshold based on a value obtained by multiplying the value obtained by subtracting a first coefficient from the previous TPI threshold by a value obtained by subtracting a second coefficient from the voltage drop of the IEGM signal.

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